"The Ebola response strategy is working, and we are beginning to see improvements," said Ban.

"But now is not the time to ease up on our efforts.... We must do everything we can to get to zero." Last month, Ban had said that with stepped up international mobilisation, the outbreak could be brought under control in 2015.

The UN Security Council has declared the Ebola outbreak a threat to international security and peace, and US Ambassador Samantha Power paid a visit to West Africa in October.

Concern has focused recently on Sierra Leone, where the number of infections continues to surge, and deep in the forested areas of Guinea. However, the caseload has decreased in Liberia.

Sierra Leone on Wednesday imposed strict measures including a ban on New Year revelries, travel restrictions and door-to-door monitoring in a bid to stem the spread of Ebola.

"Our country is at war with a vicious enemy that is taking the lives of our people," Sierra Leone President Ernest Bai Koroma said in a radio address announcing the measures.

Ban is due to meet with leaders in all five countries, along with UN staff and health care workers on the frontlines of the fight against Ebola.